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Examining Optimal Sight Distances at Rural Intersections

From 2008 to 2012 in Minnesota, nearly 42% of all severe crashes that occurred at intersections were associated with fatal and serious injuries, making them a critical focus area of the 2014 Strategic Highway Safety Plan. Crashes are often more severe at unsignalized rural intersections with high speed and volume, especially with vehicles running stop signs (Preston, 2015). Drivers on minor roads must assess traffic gaps to safely cross, but studies indicate that drivers often underestimate the approach speed of oncoming vehicles. This results in an overestimation of vehicle arrival time (e.g., Hancock & Manser, 1997). Limited visibility has been tied to drivers choosing smaller oncoming vehicle gaps, increased stop violations, and encroaching into pedestrian crossings at signalized intersections (Yan & Richards, 2010). However, simply increasing sight distance to produce maximum visibility may not result in linear gains in safety. Increasing sight distance has been shown to only improve driver confidence, but not safety at rail crossings (Ward & Wilde, 1996) and result in poor peripheral detection of vehicles on collision courses with drivers because they appear static (Uchida et al., 2001). Establishing a proper lower- and upper-limit for visibility at rural intersections will not only minimize cost and labor to ensure clearing and grubbing efforts are efficient, but may also maximize driver safety and behavior around rural thru-STOP intersections to reduce serious injury and fatal crashes statewide. This simulated driving study will examine intersection visibility and other critical factors which influence driver behavior and recommend visibility standards for rural thru-STOP intersections in Minnesota.